Rules vs. principles. GAAP is rules based, which means that it is full of very specific rules for how to treat a large number of transactions. This results in some gaming of the system, as users create transactions that are intended to manipulate the rules in order to achieve better financial results. The rules basis also results in very large standards, so that the text of GAAP is much larger than the text of IFRS. IFRS is principles based, so that general guidelines are set forth, and users are expected to use their best judgment in following the principles.

LIFO inventory. GAAP allows a company to use the last in, first out method of inventory valuation, while it is prohibited under IFRS. LIFO tends to result in unusually low levels of reported income, and does not reflect the actual flow of inventory in most cases, so the IFRS position is more theoretically correct.

Write down reversals. GAAP requires that the value of an inventory asset or fixed asset be written down to its market value; GAAP also specifies that the amount of the write-down cannot be reversed if the market value of the asset subsequently increases. Under IFRS, the write-down can be reversed. The GAAP position is excessively conservative, since it does not reflect positive changes in market value.

Development costs. GAAP requires that all development costs be charged to expense as incurred. IFRS allows certain of these costs to be capitalized and amortized over multiple periods. The IFRS position may be too aggressive, allowing for the deferment of costs that should have been charged to expense at once.

We have noted some of the more significant differences between GAAP and IFRS. There are hundreds of smaller differences within each of the major topics of accounting, which are constantly being adjusted as the two standards are updated.